The present invention relates to an attractant composition for Colorado potato beetles, which composition contains a carrier material and a Colorado potato beetle attracting effective amount of (S)-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol. The present invention also relates to a method for attracting Colorado potato beetles to an object or area, which method involves treating the object or area with a Colorado potato beetle attracting composition which contains a carrier material and a Colorado potato beetle attracting effective amount of (S)-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol.
Insect behavior is governed by complex interactions among chemical and physical signals in the environment. For example, host plant volatiles may (1) facilitate orientation of insects to potential feeding sources (Bernays, E. A., and R. F. Chapman, 1994, Host Plant Selection by Phytophagous Insects, xiii+312p, New York, N.Y., Chapman & Hall); (2) provide a mechanism for insects to avoid nonhosts (Dickens, J. C., et al., Experientia, 48: 523-524 (1992)); or (3) either enhance behavioral responses to pheromones (Dickens, J. C., Ent. exp. Appl., 52: 191-203 (1989); Dickens, J. C., et al., Naturwissenschaften, 77: 29-31 (1990)) or disrupt behavioral responses to pheromones (Dickens, J. C., et al., Experientia, 48: 523-524 (1992)). Insect-produced volatiles or pheromones attract conspecifics for mating (Cardé, R. T., and T. C. Baker, 1984, Sexual communication with pheromones, In Chemical Ecology of Insects (eds. W. J. Bell and R. T. Cardé), pp. 355-383, New York: Chapman & Hall) or disrupt behavioral responses of closely related species (Hansen, K., Physiol. Entomol., 9: 9-18 (1984); Borden, J. H., 1997, Disruption of semiochemical-mediated aggregation in bark beetles, In Insect Pheromone Research New Directions (eds. Cardé, R. T. and Minks, A. K.), pp. 421-438, New York, N.Y.: Chapman & Hall).
The existence of a sex attractant pheromone for the Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera:Chrysomelidae) has been a subject of dispute. Boiteau (Boiteau, G., Ent. exp. Appl., 47: 183-187 (1988)) considered that plant odors attracted both sexes to the crop where sexual encounters were at random. The existence of a short-range or contact sex pheromone on the elytra of female CPB that elicited copulatory behavior in males was first shown by Levinson et al. (Levinson, H. Z., et al., Naturwissenschaften, 66: 472-473 (1979)) and later verified by others (Jermy, T., et al., Ent. Exp. Appl,. 59: 75-78 (1991); Otto, D., 1996, Further evidence for the presence of a female sex pheromone in the Colorado potato beetle Leptinotarsa decemlineata Say. and its biological characterization, In Practice Oriented Results on Use and Production of Neem Ingredients and Pheromones IV (eds. H. Kleeberg and V. Micheletti), pp. 135-147, Lahnau, Germany: Trifolio-M GmbH).
Prior to the work of Boiteau (1988) cited above, DeWilde et al. (DeWilde, J.; et al., Netherlands J. Plant Pathol., 75: 53-57 (1969)) observed that female emissions enhanced the anemotactic response of males in a laboratory behavioral bioassay. Experiments by Levinson at al. (Levinson, H. Z., et al, Naturwissenschaften, 66: 472-473 (1979)) showed that males responded differentially to male and female extracts from a distance of 8 mm. These observations could not be verified in a different behavioral assay in which male CPB did not show any sign of percepting the presence of females kept in small cages. Later Edwards and Seabrook (Edwards, M. A., and W. D. Seabrook, Canad. Entomol., 129: 667-672 (1997)) demonstrated that males move upwind towards females from a distance of at least 50 cm. Their results were based on greenhouse studies where all possible sex combinations placed on potted potato plants were tested; however, only 22% (11 of 49) of male beetles moved toward the female containing plant.
Based on laboratory behavioral studies in which antennal segments were selectively extirpated, olfactory receptors for the sex attractant pheromone in male CPB were thought to be located on the terminal and penultimate antennal segments (DeWilde, J., et al., Netherlands J. Plant Pathol., 75: 53-57 (1969)). Electroantennograms elicited by pentane extracts of female beetles were nearly twice as large as those elicited by extracts of males or potato foliage (Levinson, H. Z., et al, Naturwissenschaften, 66: 472-473 (1979)). Dubis et al. (Dubis, E. E., et al., Comp. Biochem. Physiol., 87A: 839-843 (1987)) demonstrated chemical differences in cuticular hydrocarbons of male and female beetles; such differences could function in the recognition of females by males and as a releaser of copulatory behavior.
We report herein the discovery of a male-specific compound ((S)-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol (CPB I)) released by males feeding on potato plants; this compound is absent in collections of volatiles from females feeding on potato plant. Both male and female CPB are attracted to CPB I in laboratory behavioral bioassays. Since the accepted paradigm for chrysomelid beetles in general (Mayer, M. S., and J. R. McLaughlin (1991), Handbook of Insect Pheromones and Sex Attractants, Boca Raton, Fla.: CRC Press, 1083 pp.), and the CPB in particular (DeWilde, J., et al., Netherlands J. Plant Pathol., 75: 53-57 (1969); Edwards, M. A., and W. D. Seabrook, Canad. Entomol., 129: 667-672. (1997), was a female-produced attractant pheromone, our discovery of a male-produced pheromone in CPB surprisingly breaks the previous paradigm and provides a new model for chemical communication in these insects.